United is now the first U.S. airline to give customers non-binary gender options while booking their flights, the carrier announced Friday.

"United is excited to share with our customers, whether they identify along the binary of male or female or not, that we are taking the steps to exhibit our care for them while also providing additional employee training to make us even more welcoming for all customers and employees," United's Chief Customer Officer Toby Enqvist said in a statement.

The airline has worked with LGBTQ organizations The Human Rights Campaign and The Trevor Project on training employees in conjunction with these updates. Such training includes the use of preferred pronouns.

"By providing non-binary gender selection for ticketing and the gender-inclusive honorific 'Mx' in user profiles, United Airlines is taking an important step forward for non-binary inclusion," Beck Bailey, acting director of the Workplace Equality Program at the Human Rights Campaign, added in the same statement.

Fly how you identify. Our new non-binary gender options are now available.

Amit Paley, CEO & Executive Director of The Trevor Project, a national organization geared toward crisis and suicide prevention efforts for LGBTQ youth, said in the statement: "We are thrilled to bring Trevor's expertise on the mental health of LGBTQ people to United to ensure its employees maintain safe and inclusive spaces for LGBTQ employees and guests."

United's announcement comes after two big trade groups – Airlines for America in the USA and the global International Air Transport Association – recently approved a new international best-practices standard that suggests accommodation for travelers using "non-binary IDs."

The suggested standard would create an option for "unspecified" or "undisclosed" for passengers booking tickets. That option would be in addition to the options for "male" or "female."

This standard was said to become effective June 1, but it was up to individual airlines to make the option available to their booking platforms.

The nation's five biggest U.S. airlines – American, Delta, United, Southwest and Alaska airlines – all previously told USA TODAY that they plan to implement the trade groups’ suggestion.

Delta spokesperson Kate Modolo told USA TODAY in a statement: "As part of Delta’s ongoing efforts to reflect inclusivity and respond to the needs of our diverse customer population, we are planning to offer a non-binary gender option during the booking process." The statement reflects what the airline told USA TODAY in February.

Alaska Airlines is planning on including this option but doesn't have an update on timing. Spokesperson Ann Johnson referred USA TODAY to the airline's original statement: "As part of our values of having a culture of inclusion for all, we are planning to implement a non-binary gender option for guests to select in the booking process."

Southwest Airlines is working on such an option, as well, also echoing an earlier statement. "Please know that while we don’t have a timeframe to share, Southwest is currently investigating solutions and the technical requirements needed to provide our customers non-binary gender marker options during the booking process," spokesperson Michelle Agnew told USA TODAY.

USA TODAY has also reached out to American Airlines for any updates to its previous plans to implement similar booking changes.

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